Background <p>The ichthyoses are a group of rare, dermatological conditions characterised by dry, thickened scales across the body and impaired skin barrier function. Although ichthyosis may be acquired, the majority of cases are congenital and caused by specific genetic variants. The ichthyoses can cause multiple skin-related issues (e.g. increased risk of infection) and can also have substantial downstream effects on mental health and quality of life; moreover, they are commonly comorbid with a range of medical conditions. Although the symptoms associated with the various ichthyosis subtypes have been reasonably well-defined, how these change over time, and how they compare to one another, has not yet been systematically investigated. Using an online survey approach, we obtained detailed quantitative and qualitative data from adults diagnosed with congenital ichthyosis who self-reported on their skin-related and medical symptoms, and the impact of these, across six time periods; we also obtained data on factors self-reported to contribute to changing health over time, and on participants’ future health concerns.</p> Results <p>We recruited a total of 222 adult participants diagnosed with a range of ichthyosis subtypes: ichthyosis vulgaris (<i>n</i> = 86), autosomal recessive congenital ichthyosis (<i>n</i> = 67), X-linked ichthyosis (<i>n</i> = 34), epidermolytic ichthyosis (<i>n</i> = 30) and Netherton syndrome (<i>n</i> = 8). We showed that the ichthyoses have a lifelong impact on quality of life, particularly for more severe subtypes, but that this diminishes over time and correlates with skin health. Participants with the more severe forms of ichthyosis self-reported adverse effects throughout life on homeostatic health (e.g. ability to maintain body temperature) and in mid-late middle age on mobility and autoimmune health. These participants also reported consistently relatively poor mental health across life, whereas participants with milder forms of ichthyosis reported more variable mental health outcomes across life. Cardiac and metabolic health were generally regarded as being reasonable throughout life across all ichthyosis subtypes. Participants were most concerned about future worsening of their skin condition and associated medical conditions.</p> Conclusions <p>Our data provide new information on how ichthyosis subtypes vary, and compare, at different ages. This information is important for identifying optimal intervention points, and for improving genetic counselling processes.</p>